Method for producing a metal die or mold

ABSTRACT

A method for producing a metal die or mold including the steps of placing a layer of sintering powder, such as iron, copper, tungsten carbide or titanium carbide, in a frame or box, placing in contact with the sintering powder a pattern made of an infiltrant metal, such as copper, lead, cobalt, nickel, iron or alloys thereof, having a lower melting point than that of the sintering powder, the pattern corresponding in configuration to that of the cavity surface of the desired die, heating the powder together with the pattern in the frame to sintering temperature, whereby to sinter the powder and infiltrate the infiltrant metal forming the pattern into the powder, and cooling so as to obtain a hardened sintered mold having a surface whose configuration complements that of the pattern surface.

United States Patent Umehara et al.

[451 Dec. 19, 1972 [54] METHOD FOR PRODUCING A METAL DIE OR MOLD [72]Inventors: Hanji Umehara; Takashi Kimura; l-liroshi Hamamoto, all ofNagoya, Japan [73] Assignee: Kabushiki Kaisha Toyoto Chuo Ken- 21 App].No.: 72,380

[30] Foreign Application Priority Data Sept. 22, 1969 Japan ..44/75691[52] US. Cl ....75/200, 29/l82.l [51] Int. Cl. ..B22f 3/26 [58] Field ofSearch .249/135, 134; 164/138; 75/200, 7 75/208; 29/1821 7/1956 Goetzelet al. ..29/182.1

FOREIGN PATENTS OR APPLICATIONS 984,881 7/1951 France PrimaryExaminerCarl D. Quarforth Assistant Examiner-Bl Hunt Attorney-Berman,Davidson & Berman 57] ABSTRACT A method for producing a metal die ormold including the steps of placing a layer of sintering powder, such asiron, copper, tungsten carbide or titanium carbide, in a frame or box,placing in contact with the sintering powder a pattern made of aninfiltrant metal, such as copper, lead, cobalt, nickel, iron or alloysthereof, having a lower melting point than that of the sintering powder,the pattern corresponding in configuration to that of the cavity surfaceof the desired die, heating the powder together with the pattern in theframe to sintering temperature, whereby to sinter the powder andinfiltrate the infiltrant metal forming the pattern into the powder, andcooling so as to obtain a hardened sintered mold having a surface whoseconfiguration complements that of the pattern surface.

23 Claims, 10 Drawing Figures METHOD FOR PRODUCING A METAL DIE OR MOLDBACKGROUND OF THE INVENTION This invention relates to a process for themanufacture of a metal die or mold of metal powder sintered and cooledto form a die in its broadest sense, such as a casting mold, a pressingdie, or a die-cast mold.

DESCRIPTION OF THE PRIOR ART Hitherto, the manufacture of metal dies andmolds has been carried out by engraving, in which steel is machined intoa desired mold shape and size by a machine tool; by precision casting,using a lost wax method mold, shell mold, or the like; or by specialprocessing in which the mold material is treated by chemical etching orelectrical spark discharge to attain a desired shape.

These known processes require, however, complex manufacturing steps,highly skilled workmen and a great deal of time, and, accordingly, arevery expensrve.

SUMMARY OF THE INVENTION The present invention provides for themanufacture of a metal die or mold by a sintering process which obviatesthe disadvantages of the conventional methods briefly outlined above,and which can be performed at low cost, the process being simpler,requiring no finishing machining, and very little skill or training onthe part of the workmen.

The improved method comprises the steps of placing in an outer frame asintering powder such as iron, copper, tungsten carbide, titaniumcarbide or mixtures thereof, placing in contact with the sinteringpowder, a pattern made of an infiltrant metal such as copper, lead,cobalt, nickle, iron, or alloys thereof, having a lower melting pointthan that of the sintering powder, the pattern corresponding inconfiguration to that of the cavity surface of a desired die, placingthe frame together with the pattern and the sintering powder in asintering furnace, and heating the same to sintering temperature. Duringthe sintering operation the infiltrant metal pattern melts andinfiltrates entirely into the sintered metal powder. Upon cooling, theresultant produce is a hardened sintered mold or die having a cavityhaving a shape and size corresponding to the surface of the pattern atthe portion where the pattern was disposed. In the finished product, theinfiltrated metal also serves to strengthenand reinforce the bonding ofthe sintered material so as to provide a die or mold having a greaterstrength than if the product was formed of the sintered material alone.If desired, the sintering material may be compressed, either before orduring the sintering, so as to increase the density of the sintered dieproduct, Furthermore, a heat-resistant parting agent may be coated onthe surface of the charged sintering powder except at the portionscovered by the pattern, and additional sintering powder may be placedthereover, so that the resulting product after sintering is a splitmetal mold consisting of an upper portion and a lower portion having amolding surface therebetween corresponding to the surface of thepattern.

It will be apparent from the above, that a primary object of the presentinvention is to provide a method for producing a metal die or mold suchas a casting mold or a pressing die, by sintering a metal powdermaterial.

Another object of the invention is to provide a method for producing ametal die or mold without machining.

Still another object of the invention is to provide a method forproducing a metal die or mold having precise dimensions.

A further object of the invention is to provide a method for producing adie or mold having high strength.

Astill further object of the invention is to provide a method forproducing a metal die or mold which is easy to follow, inexpensive,provides consistent results, and is commercially practicable.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features that are consideredcharacteristic of this invention are set forth withparticularity in theappended claims.

The invention itself, however, both as to its organization and itsoperation, together with additional objects and advantages thereof, willbest be understood from the following descriptions of specificembodiments when read in connection with the accompanying drawings,wherein like reference characters indicate like parts throughout theseveral figures, and in which:

' FIGS. 1 to 4 illustrate a first embodiment of the invention;

FIG. 1 is a cross-sectional view of a container formed by a pressingdie;

FIG. 2 is a cross-sectional view of a pressing metal die for forming thecontainer of FIG. 1;

FIG. 3 is a fragmentary perspective view of a pattern used in producingthe pressing die of FIG. 2;

FIG. 4 is a cross-sectional view of the embodiment consisting of acompressed metal powder with the pattern of FIG. 3 arranged therein;

FIG. 5 is a cross-sectional view of the second embodiment of theinvention consisting of the compressed metal powder with a patternarranged thereon;

FIGS. 6 to 9 illustrate a third embodiment of the invention;

' FIG. 6 is a perspective view of a pattern used in making a castingmold;

FIG. 7 is a cross-sectional view of an embodiment for making a castingmold comprising compressed metal powder with the pattem of FIG. 6arranged therein;

FIG. 8 is a transverse section taken along the line VIII-VIII of FIG. 7;

FIG. 9 is a cross-sectional view of the casting mold resulting from theprocess of this embodiment; and

FIG. 10 is a cross-sectional view of another pattern which may be usedin the process illustrated in the third embodiment.

DESCRIPTION OF PREFERRED EMBODIMENTS The first embodiment of theinvention is illustrated in FIGS. 1 to 4. This embodiment concerns themanufacture of a pressing die of sintered iron powder having a lower die21, a blank holder 22, and a punch 23, as shown in FIG. 2. This type ofdie can be used for making a container such as the U-shaped container 1as shown in FIG. 1. In manufacturing this type of die, a pattern 10 madeof copper, as shown in FIG. 3, is employed. The pattern comprises acylinder 11 with a closed bottom and a flanged portion 12 provided inthe middle of the cylinder. The flanged portion 12 has a configurationlarger than a sheet material used for press-forming the container 1, andthe cylinder 11 has the same diameter and thickness as those of thecontainer 1.

The method of manufacturing the pressing die of FIG. 2 is illustrated inFIG. 4. A lower filler layer 51 of iron powder is first placed on acompression punch 41 in the cylindrical molding frame 3. The pattern 10is then placed on top of the lower filler layer 51 in intimate contacttherewith. An upper filler layer 52 of iron powder is thenplaced on topof the pattern 10 so as to fill the space interior of the cylinder 11and also the space exterior of the cylinder 11 above the flanged portion12. The iron powder is then compressed and molded under a pressure of2-tons per square centimeter between the compression punches 41 and 42.The upper filler layer 52 preferably extends for a short distance abovethe top of the cylinder 11 so as to prevent curvature or deformation ofthe cylindrical part which would be caused by the compression of thepunch 42 directly applied to the cylindrical part. The compressed ironpowder compact containing the pattern 10 is then sintered in anatmosphere of nitrogen for 60 minutes at l120 C in a sintering furnace.

Since the melting point of copper is 1083 C and thus below thetemperature used for sintering, the copper pattern melts during thesintering operation. The molten copper infiltrates into the spaces inthe sintered iron powder by a capillary action, thereby strengtheningthe bonding of the iron powder so that the finished product has agreater strength than a sintered product from iron powder alone. Theinfiltration of'the molten copper into the sintered iron powder alsoleaves a cavity in the sintered material corresponding in dimensions andshape to the pattern 10 at the portion where the pattern 10 has beenlocated. Following the sintering operation, the sintered product is thencooled.

The thus obtained sintered product is in the form of the pressing die asshown in FIG. 2, having a lower die 21 corresponding to the lower fillerlayer 51 of iron powder, and a blank holder 22 and punch 23corresponding to the upper filler layer 52 of iron powder. The lower die21 has surfaces 211 and 212 formed from the outer contour of the lowerpart of the cylinder 11 below the flange portion 12, and also an uppersurface 213 formed from the lower surface of the flange portion 12. Theblank holder 22, which is in the form of a thick-walled cylinder, has aninner peripheral surface 222 formed from the outer contour of the upperportion of the cylinder 11 above the flange portion 12, and a lowersurface 223 formed from the upper surface of the flanged portion 12. Thepunch 23 has lower surfaces 231 and 232 formed from the inner contour ofthe lower part of cylinder 11 below the flange portion 12 and a lateralperipheral surface 232 formed from the inner contour of the upper partof the cylinder 11 above the flanged portion 12.

In making the finished pressing die as shown in FIG. 2, the portion ofthe upper filler layer 52 above the space formed by the pattern 10 ispreferably cut away long the dotted line as shown in FIG. 4, and theupper ends of the blank holder 22 and punch 23 are respectivelyconnected to pressing means 24 and 25. The thus obtained pressing die isuseful for making an article such as the U-shaped container 1 as shownin FIG. 1.

As illustrated in FIG. 4, the peripheral edge of the flange portion 12of the pattern is closely fitted to the cylindrical molding frame 3. Itis also possible, however, to form the inner part of the molding frame 3wider in section than the area of the flanged portion 12. In this casethe lower filler layer 51 is filled up to the surface of the flangeportion 12 of the pattern with the iron powder, and the lower fillerlayer 51 outside the flange portion 12 is coated on the surface with analumina powder parting agent. Thereafter, the upper filler layer 52 canbe filled with the iron powder. After sintering, the portions outsidetheflanged portion 12 of the pattern are removed or mechanicallymachined in a shape so as to avoid disturbance against the pressed work.

The second embodiment of the invention, as shown in FIG. 5, concerns themanufacture solely of the lower die 21 of the first embodiment.

A heat-resistant ceramic molding box 31 which has been coated withalumina powder parting agent on the inside, serving for a molding frame,is filled with iron powder at the bottom thereof to form the lowerfiller layer 51. A copper pattern 101 is then mounted on theabove-described molding box over the lower filler layer 51 and inintimate contact therewith. The pattern 101 is similar to the lower halfof the pattern 10 of the first embodiment, and is made by taking off theupper cylinder from the flanged portion 12 of the pattern 10. On top ofthe pattern 101 is then placed magnesia powder which forms the upperfiller layer 53. Pressure of two tons per square centimeter is thenapplied from the upper filler layer 53 through a plate 54. Aftercompression molding, the plate 54 and the magnesia powder (upper fillerlayer 53) are removed. The lower filler layer 51 and the pattern 101 arethen placed in a sintering furnace together with the molding box 31 andsintered in an atmosphere of nitrogen for 60 minutes at 1120 C. Thesintered product, after being cooled and taken out of the molding box31, is in the form of the lower mold 21.

During the sintering operation as previously described, the copper usedfor the pattern infiltrates into the sintered material. Therefore, amolding surface is formed on the upper surface of the sintered materialhaving the same dimensions and shape as the lower surface of thepattern.

The described magnesia powder acts as a compression medium forpreventing the deformation of the pattern 101 in the compression of thelower filler layer 51. Alternatively, the compression molding can becarried out without the magnesia powder by means of a punch of the sameshape as the upper surface of the pattern.

In the second embodiment as described, since only a lower mold isformed, the pattern may be thinner than in the first embodiment, unlessit is desired to increase the strength of the pressing die. By makingthe pattern thinner, it is possible to economize the infiltrant metaland facilitate the manufacture of the pattern.

The third embodiment of the invention is illustrated in FIGS. 6 to 9 andconcerns the manufacture of a casting mold as shown in FIG. 9 forcasting a product corresponding in shape to the pattern 6. The pattern6, as

shown in FIG. 6, is made of copper and has a gate stick 61 and aflow-off stick 62 on the upper edge of the cup 60 having a dish-shapeand having a flat bottom. As shown in FIGS. 7 and 8, a molding frame 31having a bottom plate is first coated on the inner peripheral surfacethereof with alumina powder. The bottom of the molding frame 31 isfilled with a sintering powder mixture comprising 97 percent iron and 3percent graphite, by weight. The pattern 6 is then mounted on thesintering powder and additional powder is then added to the upper edgeof the pattern 6 so as to form the lower filler layer 71. Four copperpatterns 65 are then imbedded in the sintering powder at four locationsaround the pattern 6 for molding guide portions. The patterns 65 have acup-shaped construction, with their upper ends respectively in the samehorizontal plane as the upper surface of the lower filler layer 71. Theupper surface of the lower filler layer 71 is then coated with aluminapowder parting agent 8, upon which additional sintering powder is addedto form the upper filler layer 72.

The sintering powderis then compressed under a load of one ton persquare centimeter from the upper filler layer 72. The thus compressedsintering powder containing each pattern is then placed in a sinteringfurnace together with the molding frame 31, presintered for two hours at900 C, and then further heated for 60 minutes at 1 120 C to infiltratethe copper of the patterns into the sintered product. After cooling, thesintered product is taken out of the molding frame 31 to form thecasting mold shown in FIG. 9, having a lower mold 721 and an upper mold722.

The resulting casting mold is a split mold consisting of upper and lowermold halves. The lower mold 721 has a casting mold surface with the sameshape and dimensions as the lower surface of the pattern 6 and also hasguide holes 766 for receiving the guides 765 of the upper mold 722. Theupper mold 722 has a casting mold surface with the same shape anddimensions as the upper surface of the pattern 6 and also has a gate761, a tapping 762 and guides 765. Therefore, the guides 765 of theupper mold 722 may be inserted into the guide holes 766 of the lowermold 721 on which is laid the upper mold 722, whereby the inner surfaceforming the cavity in the split mold will constitute the casting moldsurface and have the same shape and dimensions as the pattern 6.

In the above example, the alumina powder parting agent was coated onlyon the lower filler layer 71. For convenience, however, the patterns 6and 65 may be coated on the surface with parting agent, if desired. Thepre-sintering operation can be employed for strengthening the bonding ofthe sintering powder before regular sintering, thereby resulting inincreased strength of the casting mold after sintering.

In this embodiment, since the upper and lower molds are manufacturedsimultaneously as a composed split mold, even if the molds have someroughness on the contact surfaces 9 of the upper and lower mold halves,these contact surfaces 9 perfectly fit with each other. Consequentlyleakage of molten metal from the mold is not likely to occur. Thereforeit is not required to smoothly machine the contact surface, such as inthe case where the upper an lower mold halves are separately andindividually manufactured.

FIG. 10 shows a cross-section of a modified embodiment of the patternused in the third embodiment as described above. This pattern differsfrom the one previously described in consisting of a portion 60 formingthe casting cavity and portions 65' forming the guides, which portionsare connected with a thin sheet 69 to formthe split in the upper andlower mold halves. The upper and lower mold halves can be molded at thesame time without use of the alumina'pow'der parting agent. In this casethe pattern 60' forming the casting cavity will be formed thicker thanthe cup 60 of the pattern as shown in FIG. 6 by the thickness of thethin sheet 69 forming the split surfaces of the upper and lower moldhalves. v

The casting molds and pressing dies made in accordance with thisinvention may be used repeatedly without any modification appearing inthe shape and size of both moldsand dies and the products produced byuse of the molds and dies.

In carrying out the method of the present invention, the metal powderused as the sintering material may be iron, copper, tungsten carbide,titanium carbide or the like. The infiltrant metal used to form thepattern must have a melting point lower than the sintering temperatureof the sintering material. The sintering conditions will, of course,vary with the particular materials used for the sintering material andfor the pattern. For example, if a ferrous metal powder whose mainingredient is iron or iron-carbon is used as the sintering powder, thenthe infiltrant metal used for forming the pattern should be eithercopper, at or copper alloy such as percent copper 5 percent manganesealloy, a 97 percent copper 3 percent cobalt alloy, or the like. Typicalsintering conditions for these materials would be 60 minutes at 1 C inan atmosphere of nitrogen under a compression pressure of 2 tons persquare centimeter. If copper powder whose main ingredient is copper, ora copper alloy, is used as the sintering powder, then the infiltrantmetal used for forming the pattern should be lead, or lead alloy such asa 50 percent lead 50 percent tin alloy, an 82 percent lead 18 percentcadmium alloy or the like, with typical sintering conditions being 60minutes at 500 C in an atmosphere of hydrogen and under a compressionpressure of 0.5 ton per square centimeter. If a metal powder whose mainingredient is tungsten carbide is used as the sintering material, thenthe infiltrant metal used for forming the pattern should be iron cobalt,nickel or the alloy thereof, with typical sintering conditions being 60minutes at l550 C in an atmosphere of hydrogen and under a compressionpressure of 1 ton per square centimeter. If a metal powder whose mainingredient is titanium carbide is employed as the sintering material,then the infiltrant metal used for forming the pattern should be iron,cobalt nickel, a or the alloy thereof such as 95 percent nickel 5percent molybdenum alloy, with typical sintering conditions being 60minutes at 1550 C in an atmosphere of hydrogen and under a compressionpressure of one ton per square centimeter.

The pattern used in the present invention will have the same dimensionsand shape as the molding surface of the metal die or mold desired. Thewhole pattern may be made of the infiltrant metal as shown in the aboveexamples. If the pattern is of large volume, it may have a cavity in theinterior thereof or the pattern may be formed of ceramic or the likeheat-resistant material serving for the base and lined with infiltrantmetal to prevent said pattern from deforming by the pressure throughpress molding. In the latter case, the ceramic base may be taken offafter sintering. A sheet of infiltrant metal may be employed between theupper and lower mold halves or guides and guide holes which are notdirectly connected to the molding surface of the metal die or mold, asthe pattern 65 in the third embodiment. As shown in the thirdembodiment, it is possible to form a boundary by coating thereon aheatresistant parting agent such as alumina or magnesia. Such partingagent can be coated on the abovedescribed thin sheet so as to preventthe sintering on the boundary.

In the method of the present invention, compression molding of thesintering material prior to sintering increases the density and strengthof the final die or mold. in the event that the sintered product is notrequired to have high density and strength, sintering can be donewithout the compression molding of the metal powder or with compressionmolding under low pressure. If the sintering material is not compressedor is compressed to only a slight degree, then it is preferred to carryout the sintering operation in a molding box which is resistant to thesintering temperature, as shown in the second and third embodiments, soas to prevent collapse of the metal powder prior to sintering.

The method of the present invention can be applied not only to themanufacture of press die and casting molds, but also to diecastingmolds, molds for plastic, glass or rubber molding, as well as othergeneral metal molds. It is likewise apparent that by proper use ofparting compounds or infiltrant metal sheets arranged on the surfaces asdesired, it is possible by means of the present invention to makevarious types of multi-split molds such as a triple or quadruple splitmold.

As will be apparent from the above description and embodiments, themethod of manufacturing metal dies or molds in accordance with thepresent invention provides a vast improvement over prior methods in thatit does not require complicated machining procedures nor particularskill, but is simpler, less time consuming, and more economical.Furthermore, due to the strengthening and reinforcing effect of theinfiltrant metal being infiltrated into the sintered metal, theresulting metal die or mold has improved strength and quality.

Although certain specific embodiments of the invention have been shownand described, it is obvious that many modifications thereof arepossible. The invention, therefore, is not intended to be restricted tothe exact showing of the drawings, and description thereof, but isconsidered to include reasonable and obvious equivalents.

What we claim is:

l. A method for producing a metal die or mold composed of a sinteredbody with a hardened mold surface, comprising making a layer ofsintering powder selected from the group consisting of iron, iron alloy,copper, copper alloy, tungsten carbide and titanium carbide in a framefor forming said sintered body, placing a pattern having a surface ofselected configuration made of infiltrant metal with a lower meltingpoint than that of said sintering powder on said layer to contact saidpattern surface with said layer for shaping said layer with a surfacecomplementing said pattern surface, heating said layer and patternwithin said frame to a sintering temperature to sinter said powder andto infiltrate said infiltrant metal forming said pattern into saidpowder, and cooling so as to obtain a sintered mold having a hardenedsurface whose configuration complements that of said pattern surface.

2. A method of producing a metal die or mold according to claim 1,wherein further comprising removing said hardened and sintered die ormold from said frame after cooling.

3 A method according to claim 1, wherein said sintering powder isferrous metal powder selected from the group consisting of iron powderand iron-carbon powder, and said pattern is made of one metal selectedfrom the group consisting of copper, copper-manganese alloy, andcopper-cobalt alloy.

4. A method according to claim 1, wherein said sintering powder iscopper powder or copper alloy powder, and said pattern is made of onemetal selected from the group consisting of lead, lead-tin alloy, andlead-cadmium alloy.

5. A method according to claim 1, wherein said sintering powder istungsten carbide powder and said pattern is made of one metal selectedfrom the group consisting of iron, cobalt, nickel and the alloy thereof.

6. A method according to claim 1, wherein said sintering powder istitanium carbide powder and said pattern is made of one metal selectedfrom the group con sisting of iron, nickel, cobalt or the alloy thereof.

7. A method according to claim 1, wherein said sintering powder layer ispresintered at a lower temperature than the melting temperature of theinfiltrant metal forming said pattern before heating to sinter saidsintering powder layer completely.

8. A method according to claim 1, wherein said powder layer iscompressed before heating to sinter said powder layer.

9. A method according to claim 8, wherein a pressure medium layer ofheat-resistant powder such as magnesia powder layer is placed on saidsintering powder layer such that the upper surface is made plane, andsaid sintering powder is compressed through said pressure medium layer,then said pressure medium layer is removed before heating to sinter saidsintering powder layer.

10. A method according to claim 1,, wherein said pattern has a thinplate member surrounding said selected configuration part to beoverspread on the upper surface of said sintering powder layer exceptthe area covered by said selected configuration part.

11. A method according to claim 1, wherein said pattern has a core madeof a heat-resistant material such as ceramic and covered by saidinfiltrant metal and said core is removed from the mold after sintering.

12. A method according to claim 1, wherein a heatresistant parting agentis placed as a thin layer between said frame and said layer of sinteringpowder.

13. A method according to claim 12, wherein said heat-resistant partingagent is selected from the group consisting of alumina and magnesia.

14. A method according to claim 1, wherein said layer of sinteringpowder substantially completely surrounds said pattern whereby thecompleted mold has a configuration complementing that of the pattern.

15. A method according to claim 14, wherein a plurality of said patternsis provided in said frame, said powder is disposed in said frame abouteach of said patterns in a plurality of layers separated from oneanother by thin layers of infiltrant metal with a lower melting pointthan that of said sintering powder, whereby upon completion of sinteringand cooling a plurality of metal molds is obtained constituting a setand which together have the configuration of the pattern immersed insaid layers of sintering powder.

16. A method for producing a set of metal dies or molds composed of asintered body with a hardened mold surface, comprising making a firstlayer of sintering powder selected from the group consisting of iron,iron alloy, copper, copper alloy, tungsten carbide and titanium carbidein a frame for forming said sintered body, placing a heat-resistantparting agent as a thin layer on the upper surface of said first layer,placing a pattern having a surface of selected configuration made ofinfiltrant metal with a lower melting point than that of said sinteringpowder on said layer to contact said pattern surface with said firstlayer for shaping said first layer with a surface complementing saidpattern surface, making a second layer of said sintering powder on saidpattern and layer of parting agent to contact the remaining surface ofsaid pattern with said second layer of sintering powder before heatingfor sintering, heating said first and second layers and pattern withinsaid frame to a sintering temperature to sinter said powder and toinfiltrate said infiltrant metal forming said pattern into said powder,and removing said hardened, sintered dies or molds from said frame aftercooling so as to obtain a set of metal dies or molds.

17. A method according to claim 16 wherein said pattern has a thin platemember surrounding said selected configuration part, said thin platemember is disposed between the first and second layers of sinteringpowder and said thin layer of parting agent is placed between said firstand second layers of sintering powder.

18. A method according to claim 16 wherein a plurality of patterns forguide portions having U-shaped section and being made of infiltrantmetal with a lower melting point than that of said sintering powder areembedded between said first and second layer of sintering powder,whereby guide pins and holes are formed on the counter surfaces of thedies upon completion of sintering.

19. A method according to claim 17, wherein said sintering powder isferrous metal powder selected from the group consisting of iron powderand iron-carbon powder, and said pattern and thin plate are made of onemetal selected from the group consisting of copper,

copper-manganese alloy, and copper-cobalt alloy.

20. A method according to claim 16, wherein said sintering powder isferrous metal powder selected from the group consisting of iron powderand iron-carbon powder, and said pattern is made of one metal selectedfrom the group consisting of copper, copper-manganese alloy, andcopper-cobalt alloy.

21. A method according to claim 16, wherein said sintering powder istungsten carbide powder, and said pattern is made of one metal selectedfrom the group consisting of iron, cobalt, nickel, and the alloythereof.

22. A method according to claim 16, wherein said sintering powder istitanium carbide owder and said pattern 15 made of one metal selectefrom the group mm *s 'mtes 519 mm? eFFieE UER'EWMATE e1 eemeemem PatentNo. 3 7O6,55O Dated December 19 1972 Inventor(s) HANJI UMEHARA, TAKASHIKIMURA & HIROSHI HAMAMOTO It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

The name of the Assignee is changed to read KABUSHIKI KAESHA TOYOTA CHUOKENKYUSHO.

Signed and sealed this 29th day of May 1973.

(SEAL) Attet:

EDWARD M FLETCHER ,JR ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM P0405? (0459) USCOMM-DC scam-poo a ".5. GOVERNNENTPIINTIflG OFFICE 3 I909 0-355-33 "UNITED *sm'rrs PATENT 'eF'FIacfE@ER'EENCATE? 0F CQRR EQTWN Patent No. 3,706,550 Dated December 19, 1972Inventor(s) HANJI UMEHARA, TAKASHI KIMURA & i-IIROSHI HAMAMOTO It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

The name of the Assignee is changed to read KABU 5H1 KI FA 1 TOYOTA CHUOKEN KY U SHO Signed and sealed this 29th day of May 1973.

(SEAL) Atteti EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents FORM PC4050 (10.69) uscoMM-Dc wave-ps9 0.5.GOVEINHIIII' PIINTING OFFICE ISO, O-JGl-SJJ "ammo sm'ree i meni emm:C'ERTENQATE oz; G@E%RI ETE@N Patent No. 3,706?55O Dated December 19,1972 Inventor(s) HANJI UMEHARA, TAKASHI KIMURA & HI'ROSHI HAMAMOTO It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

name of the Assignee is changed to read KABUSHIKI YAESHA TOYOTA CHUOKENKYUSHO.

Signed and sealed this 29th day of May 1973.

(SEAL) AtteSt:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PC4050 uscoMM-oc wave-ps9 Q U.S. GOVERNI'IIIIY 'IINI'INGOFFICE I! 0-368-331

2. A method of producing a metal die or mold according to claim 1,wherein further comprising removing said hardened and sintered die ormold from said frame after cooling.
 3. A method according to claim 1,wherein said sintering powder is ferrous metal powder selected from thegroup consisting of iron powder and iron-carbon powder, and said patternis made of one metal selected from the group consisting of copper,copper-manganese alloy, and copper-cobalt alloy.
 4. A method accordingto claim 1, wherein said sintering powder is copper powder or copperalloy powder, and said pattern is made of one metal selected from thegroup consisting of lead, lead-tin alloy, and lead-cadmium alloy.
 5. Amethod according to claim 1, wherein said sintering powder is tungstencarbide powder and said pattern is made of one metal selected from thegroup consisting of iron, cobalt, nickel and the alloy thereof.
 6. Amethod according to claim 1, wherein said sintering powder is titaniumcarbide powder and said pattern is made of one metal selected from thegroup consisting of iron, nickel, cobalt or the alloy thereof.
 7. Amethod according to claim 1, wherein said sintering powder layer ispresintered at a lower temperature than the melting temperature of theinfiltrant metal forming said pattern before heating to sinter saidsintering powder layer completely.
 8. A method according to claim 1,wherein said powder layer is compressed before heating to sinter saidpowder layer.
 9. A method according to claim 8, wherein a pressuremedium layer of heat-resistant powder such as magnesia powder layer isplaced on said sintering powder layer such that the upper surface ismade plane, and said sintering powder is compressed through saidpressure medium layer, then said pressure medium layer is removed beforeheating to sinter said sintering powder layer.
 10. A method according toclaim 1, wherein said pattern has a thin plate member surrounding saidselected configuration part to be overspread on the upper surface ofsaid sintering powder layer except the area covered by said selectedconfiguration part.
 11. A method according to claim 1, wherein saidpattern has a core made of a heat-resistant material such as ceramic andcovered by said infiltrant metal and said core is removed from the moldafter sintering.
 12. A method according to claim 1, wherein aheat-resistant parting agent is placed as a thin layer between saidframe and said layer of sintering powder.
 13. A method according toclaim 12, wherein said heat-resistant parting agent is selected from thegroup consisting of alumina and magnesia.
 14. A method according toclaim 1, wherein said layer of sintering powder substantially completelysurrounds said pattern whereby the completed mold has a configurationcomplementing that of the pattern.
 15. A method according to claim 14,wherein a plurality of said patterns is provided in said frame, saidpowder is disposed in said frame about each of said patterns in aplurality of layers separated from one another by thin layers ofinfiltrant metal with a lower melting point than that of said sinteringpowder, whereby upon completion of sintering and cooling a plurality ofmetal molds is obtained constituting a set and which together have theconfiguration of the pattern immersed in said layers of sinteringpowder.
 16. A method for producing a set of metal dies or molds composedof a sintered body with a hardened mold surface, comprising making afirst layer of sintering powder selected from the group consisting ofiron, iron alloy, copper, copper alloy, tungsten carbide and titaniumcarbide in a frame for forming said sintered body, placing aheat-resistant parting agent as a thin layer on the upper surface ofsaid first layer, placing a pattern having a surface of selectedconfiguration made of infiltrant metal with a lower melting point thanthat of said sintering powder on said layer to contact said patternsurface with said first layer for shaping said first layer with asurface complementing said pattern surface, making a second layer ofsaid sintering powder on said pattern and layer of parting agent tocontact the remaining surface of said pattern with said second layer ofsintering powder before heating for sintering, heating said first andsecond layers and pattern within said frame to a sintering temperatureto sinter said powder and to infiltrate said infiltrant metal formingsaid pattern into said powder, and removing said hardened, sintered diesor molds from said frame after cooling so as to obtain a set of metaldies or molds.
 17. A method according to claim 16 wherein said patternhas a thin plate member surrounding said selected configuration part,said thin plate member is disposed between the first and second layersof sintering powder and said thin layer of parting agent is placedbetween said first and second layers of sintering powder.
 18. A methodaccording to claim 16 wherein a plurality of patterns for guide portionshaving U-shaped section and being made of infiltrant metal with a lowermelting point than that of said sintering powder are embedded betweensaid first and second layer of sintering powder, whereby guide pins andholes are formed on the counter surfaces of the dies upon completion ofsintering.
 19. A method according to claim 17, wherein said sinteringpowder is ferrous metal powder selected from the group consisting ofiron powder and iron-carbon powder, and said pattern and thin plate aremade of one metal selected from the group consisting of copper,copper-manganese alloy, and copper-cobalt alloy.
 20. A method accordingto claim 16, wherein said sintering powder is ferrous metal powderselected from the group consisting of iron powder and iron-carbonpowder, and said pattern is made of one metal selected from the groupconsisting of copper, copper-manganese alloy, and copper-cobalt alloy.21. A method according to claim 16, wherein said sintering powder istungsten carbide powder, and said pattern is made of one metal selectedfrom the group consisting of iron, cobalt, nickel, and the alloythereof.
 22. A method according to claim 16, wherein said sinteringpowder is titanium carbide powder and said pattern is made of one metalselected from the group consisting of iron, nickel, cobalt and the alloythereof.
 23. A method according to claim 16, wherein said sinteringpowder is copper powder or copper alloy powder, and said pattern is madeof one metal selected from the group consisting of lead, lead-tin alloy,and lead-cadmium alloy.